Vettel urges Red Bull to finally fix KERS

The otherwise dominant RB7 has been slowed multiple times in 2011 as the team grapples with a custom KERS system that is smaller and less powerful than usual in order to maximise the car's aerodynamic packaging.

And with the blown exhaust clampdown now taking effect, while McLaren has come closer to the Red Bull's pace culminating in Vettel's last-lap loss to Jenson Button in Canada, the championship leader has told his team to finally get on top of KERS.

"The competition has caught up, as we have seen again," said the German on Friday, when Ferrari's Fernando Alonso was quickest in Valencia practice.

"The last races have all been close. The time has come where I need the extra power (from KERS)," Vettel is quoted by Bild-Zeitung.

Austria's laola1.at quotes him as adding: "There is no guarantee that it (KERS) will work here."

Button, who won in Canada two weeks ago when Vettel made a mistake on the final lap, thinks the 23-year-old is showing signs of cracking under pressure.

"That last race will have hurt him mentally. Hopefully that will play on his mind and give us a chance this race," said the Briton.

"It makes me smile because it shows what can happen if we put them under pressure."